1. Field of the Invention
The present invention relates to an ink jet recording method and an ink jet recording apparatus performing a recording operation by discharging a liquid such as an ink.
2. Related Background Art
For an ink discharging method of a conventional ink jet recording system in use today, there exists a method of discharging an ink droplet utilizing an electro thermal converting element (heater) as a discharge energy element and a method of discharging an ink droplet utilizing a piezoelectric (piezo) element, either of which is capable of controlling the discharge of the ink droplet by an electric signal. For example, one feature of the ink droplet discharge method using the electro thermal converting element is that, by giving the electric signal to the electro thermal converting element, the ink in the vicinity of the electro thermal converting element is instantaneously boiled, and by an abrupt growth of a bubble produced by a phase change of the ink on that occasion, the ink droplet is discharged at high speed. On the other hand, a feature of the discharge method of the ink droplet utilizing the piezoelectric element is that, by giving the electric signal to the piezoelectric element, the piezoelectric element is displaced and, by a pressure caused at the displacement time, the ink droplet is discharged. The former method has the advantages that it does not require undue space for the discharge energy generation element, the constitution of an ink jet recording head is simple, and an integration of nozzles is easy. On the other hand, this method has disadvantages such as a volume fluctuation of a flying ink droplet caused by a heat storage in the ink jet recording head of heat generated by the electro thermal converting element, and an influence exerted on the electro thermal converting element by a cavitation due to a bubble extinction.
In the ink jet recording head where a plurality of energy generation elements are formed, energy is not normally applied simultaneously to all of a plurality of energy generation elements. As a practical matter, when the electric signal is given simultaneously to the eletro thermal converting elements, because the electric current simultaneously flowing is increased, an electric power source capable of supplying a large electric current is required and the efficiency becomes poor. Further, because a voltage drop occurs in the wiring between the power source and the electro thermal converting element, the efficiency is lowered. Hence, a plurality of electro thermal converting elements are driven by being subjected to a time division.
In the ink jet recording head of a so-called edge shooter type ink does not discharge almost vertically from a discharge port facing the electro thermal converting element. Instead, the ink discharges in the direction having a certain angle (acute angle) including 0xc2x0. Because the discharge ports are arranged in a straight line, the displacement position of dots has often deviated when the time division driving was performed. For this reason, a row of discharge ports was arranged obliquely at a certain angle so that the displacement dots were made straight in a line. However, when a block driving was performed, because another block performing the discharge subsequently to the block which has finished the discharge was in the vicinity, a displacement deviation of dots was easy to observe visually.
On the other hand, in the ink jet recording head of a so-called side shooter type which discharges almost vertically from the discharge port facing the electro thermal converting element, the position of electro thermal converting elements 414 arranged on both sides of an ink supply port 415 and the position of the discharge ports are deviated only by the displacement deviation produced when the time division driving was performed as shown in FIG. 19 so that the displacement dots were made into a line. For example, in the ink jet recording head as shown in FIG. 19, and also as shown in Table 1 and Table 2, the electro thermal converting element 414 was allowed to carry a deviation of the maximum 18 xcexcm, that is, equivalent to 1200 DPI as a deviation in the X direction.
However, in the conventional ink jet recording head of the side shooter type, because the position of the electro thermal converting element is deviated, in the discharge port where the distance from the ink supply port for supplying the ink to the inside of the nozzle to the electro thermal converting element is relatively long, the time for refilling (refill) after discharging the ink is required much more and thus a high speed response has been degraded. By allowing the discharge to be performed at the timing which is not in time for refilling, a discharge defect was caused or a discharge amount was lowered.
Also, the longer the distance from the ink supply port to the electro thermal converting element, the greater the inertial resistance in the initial stage of energization of the electro thermal converting element and bubbling at the ink supply port side, and therefore a bubbling tends to grow at the discharge port side. For this reason, the ink discharge amount becomes larger than the amount discharged from the discharge port where the distance from the ink supply port to the electro thermal converting element is short and tends to be uneven, and the problem often arises that, because a discharge speed becomes relatively high, the displacement deviation cannot be accurately corrected.
Further, because a wiring resistance between the electro thermal converting element and a driving element depends on the distance from the ink supply port to the electro thermal converting element, the wiring resistance does not become uniform and an irregularity is caused to the energy required until the bubbling arises between the electro thermal converting elements. Thus, there was often the case where the energy is supplied enough for the electro thermal converting element which requires the energy most and a durability of the electro thermal converting element is lowered.
Further, in the ink jet recording head, due to evaporation of the ink from the discharge port, when the discharge starts from a non-recording state, there occurs a phenomenon referred to as a viscous plug property which leads to the discharge defect such as the non-discharge, a diminished dot where the discharge amount becomes small and the like. The viscous plug property tends to become worse for the discharge port having a long distance from the ink supply port to the electro thermal converting element as it is hard to get an ink supply when the evaporation of the ink further advances and, in particular, the smaller the liquid droplet became, the more marked influence it received. Further, particularly for the discharge port which is separated from the adjacent discharge port by deviating the position of the electro thermal converting element and the discharge port for correcting the displacement deviation, a control effect of the evaporation by the evaporation atmosphere from the discharge port was lowered, and the viscous plug property was easy to occur. In this connection, the ink evaporates from the discharge port and the density of the ink in the discharge port is raised with the result that the density of the discharged displacement dot sometimes becomes high. In the head of the side shooter type where the disposed position of the discharge port is deviated as described above and the interval between the ink supply port and the electro thermal converting element is different for each discharge port, an ink supply capacity from the ink supply port is different for each discharge port, and therefore, the density of the displacement dot is different for each discharge port and the lowering of a recording quality was sometimes caused. This problem becomes more marked as the liquid droplet size becomes smaller and the interval between the discharge port and the electro thermal converting element becomes smaller (the system where the bubble formed by the electro thermal converting element communicates with the atmosphere).
The present inventors have recognized that, rather than the technical problem (hereinafter referred to as xe2x80x9ca first technical problemxe2x80x9d) attributable to the deviation in the displacement dot by the time division driving of the electro thermal converting element arranged in a straight line as the ink discharge liquid droplet amount becomes equal to or smaller than 9 pl and further smaller than 5 pl and/or the density of the electro thermal converting elements arranged in the shape of a column becomes equal to or more than 600 DPI, the above described technical problem (hereinafter referred to as xe2x80x9ca second technical problemxe2x80x9d) attributable to the unbalance caused as a result of the fact that the distance from the ink supply port to the electro thermal converting element is allowed to be different from each electro thermal converting element so as to solve the above-described deviation has manifested itself, and this led us to make the present invention. In other words, the present invention was made as a result of attempting an optimization to solve the first technical problem and the second technical problem from an overall viewpoint.
One of the objects of the present invention is to provide the ink jet recording method and the ink jet recording apparatus wherein a driving frequency characteristic has improved.
Another object of the present invention is to provide the ink jet recording method and the ink jet recording apparatus wherein recording irregularities have been reduced and a recording quality has improved.
Still another object of the present invention is to provide the ink jet recording method and the ink jet recording apparatus wherein durability and reliability of the head has improved.
Still another object of the present invention is to provide the ink jet recording method and the ink jet recording apparatus wherein viscous plug properties have improved.
Still another object of the present invention is to provide the ink jet recording method, wherein, by using the ink jet recording head comprising the ink supply port for supplying the ink, a plurality of ink paths communicating with the ink supply port, a plurality of electro thermal converting elements arranged in an almost straight line along the longitudinal direction of the above described ink supply port which are disposed respectively inside said plurality of ink paths and generate a thermal energy to be utilized for discharging the ink and a plurality of discharge ports for discharging the ink which communicate with the above described plurality of ink paths respectively and are disposed by respectively facing the above described plurality of electro thermal converting elements, a recording is performed by disperse-driving the above described plurality of electro thermal converting elements.
Still another object of the present invention is to provide the ink jet recording apparatus, comprising the ink jet recording head which comprises: the ink supply port for supplying the ink; a plurality of ink paths communicating with the ink supply port; a plurality of electro thermal converting elements arranged in an almost straight line along the longitudinal direction of the above described ink supply port which are disposed respectively inside the above described plurality of ink paths and generate thermal energies to be utilized for discharging the ink; a plurality of discharge ports for discharging the ink which communicate with the above described plurality of ink paths respectively and are disposed by respectively facing the above described plurality of electro thermal converting elements; and a control portion for disperse-driving the above described plurality of electro thermal converting elements.
According to the present invention, an overall performance such as the driving frequency characteristic, the recording quality, the durability of the head and the viscous plug properties can be rapidly improved.